New form of matter at CERN SPS: Quark Matter but not Quark Gluon Plasma

Abstract

I argue that a new form of matter is indeed seen in Pb+Pb collisions at CERN SPS. However, this Quark Matter (QM) is different from the theoretically predicted Quark Gluon Plasma (QGP) because its effective degrees of freedom seem to be the massive (dressed) constituent quarks instead of almost massless quarks and gluons. The equation of state of QM is hard,the time of its rehadronization is short, while the equation of state of a QGP is soft and the time of its rehadronization is long. Other similarities and differences are also summarized.

Comments: Invited review talk at the IX International Workshop on Multiparticle Production Torino 2000, full version, 18 pages, 9 figures, uses espcrc2.sty